Yield Gap Estimate Of Single-season Rice In Middle-lower Yangtze Area Based On Remote Sensing Model

Rice is the most important grain crops in China.Under the background of increasing population and decreasing cultivated land area,it is necessary to understand the current situation of rice production and yield potential of rice in China.The middle-lower Yangtze area is one of the main production areas of single-crop rice in China,this area occupies an important place in the food safety guarantee system in our country,and it is of great significance to develop national food policy to estimate yield accurately in the study area.Firstly,the data of MODIS surface reflectance and snow product data are used to extract the season rice planting area.Then we using RS-P-YEC model to estimation the actual yield and the modified CASA model to estimation the potential yield of study area.Finally,the two levels of yield were used to calculate the yield gap.The main conclusions are:(1)The season rice area extracted from the data of the MODIS surface reflectance,snow cover data and land use types were used to extract the paddy areas of study area,and the statistical yearbook data was used to verify the accuracy.Compared with the provincial statistical data and the coefficient of determination is 0.9876,with county scale statistical area,the coefficient of determination R2 reached 0.7842.All of them are through the significant test at 0.01;(2)Analysis LAI,daily precipitation,daily maximum temperature and daily minimum temperature four important input parameters sensitivity of RS-P-YECmodel by changing the values in a resonable range.Sensitivity analysis results for the four variables show that LAI has the greatest influence the model simulation yield and impact on singlecrop rice yield reached 25%,which has a positive correlation with yield.While the other three meteorological factors have less influence on the model results of the model,and the daily maximum temperature has a positive effect on the yield,whereas the minimum daily temperature and daily precipitation has negative correlation with production.(3)The rice actual yield in 2006-2016 is simulated from the RS-P-YEC model,and the yield is compared with the county statistical production.The coefficient of determination R2 is 0.5243,the root mean square error RMSE is 720.85 kg/ha,MRE average relative error was 10.01%(P < 0.01).The high production areas(>10000kg/ha)are mainly distributed in Hubei and middle of Anhui,northeast Hunan,middle and north of Jiangsu.The low producing areas(<4000kg/ha)are mainly distributed in northeast Zhejiang,southwest Jiangsu and southeast Anhui.(4)The potential yield with limited of solar radiation and temperature was calculated using CASA model.The high-value area of potential yield is mainly distributed in Hunan,northern Jiangsu and southwest Anhui,and the low-value area is mainly distributed in southern Jiangsu,southeast Anhui and Zhejiang province.The highest potential yield of several years was 23304.9kg/ha which happened in 2014.In 2009 and 2013,the annual potential yield of single-season rice was lower than 20000kg/ha,and the other years were higher than 20000kg/ha.The changes of potential yield in each province show a trend of growth.(5)In terms of the yield gap of the middle-lower Yangtze area,the lowest yield gap was 12278kg/ha which happened in 2009.The yield gap of 2008,2010,2014 and 2015 was higher than 15000kg/ha.The largest yield gap of songle-season rice is located in Jiangxi,southern Hunan and northern Jiangsu.The yield gap in Hubei and south of Hunan province was low.The yield gap of single-season rice in each province is more than 55%.The changes of yield gap in each province show a trend of growth in 2006-2016.Most of the provinces show a relatively stable state before 2013,but there were significant fluctuations after 2013.